The four remaining defendants in Silicon Valley's closely watched employee hiring case -- Google, Apple, Adobe and Intel -- have agreed to a settlement, according to a new court filing.

The plaintiffs and the companies have reached an agreement to settle all individual and class claims alleged in the class-action suit, according to a letter sent Thursday to Judge Lucy Koh and signed by the attorneys for the plaintiffs and the defendants. The letter was filed in the U.S. District Court for the Northern District of California.

The amount of the settlement is confidential until it is filed with the court next month. The groups anticipate completing documentation of the proposed settlement and presenting it for the court's consideration by May 27. The case had been scheduled to go to trial on that date.

Given the size of the companies, the settlement could be massive. Previously named defendants Intuit, Lucasfilm and Pixar have already settled for about US$20 million.

"We have reached what we believe is an excellent resolution of the case that will benefit class members," said Kelly Dermody, an attorney for the plaintiffs, via email. "We look forward to presenting it to the court and making the terms available," she said.

A spokesman for Google confirmed the existence of a settlement, but declined to comment further.

Neither Apple, Adobe nor Intel immediately responded to comment.

The case accuses executives at the companies, including Steve Jobs at Apple, of entering into secret agreements not to hire each others' workers, in an effort to protect their investments. The plaintiffs, engineers and other tech workers argued that those agreements drove down their wages and restricted their mobility.

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